"This journey has been nothing short of spectacular in every way," he wrote. "But what I've realized is that the last few years of living in such a singular environment have taken a huge toll on my life and started affecting my health. My friends, what I consider to be my home, and my life are back in Silicon Valley."

The executive will be leaving in February, after the Chinese New Year, and says he plans to take some time off before starting an unspecified "new adventure" back in Silicon Valley in California.

Once the world's most valuable technology startup with a $45 billion valuation, its growth has slowed more recently, as it lost market share and failed to hit sales targets. CEO Lei Jun said at the start of 2017 that the company has grown "too fast," causing problems.

The company's smartphones are not yet available in most Western markets, where Barra — who formerly worked at Google on Android — is its most recognisable spokesperson.